The subject invention relates to a method and an apparatus for applying sealing material such as latex or adhesive to portions of flat or folded sheets, papers, bags, or the like, and more particularly to a method and apparatus for applying latex to the flap closure portion and the adjacent body portion of an envelope whereby when the latex portions are placed in overlapping relationship and pressure is applied, the envelope may be sealed.
It is to be understood that although the method and apparatus of the subject invention will be described with respect to the application of sealing materials, in general, it has particular application to a method and apparatus for the appliction of latex to an envelope flap and the cooperating portion of the envelope body in order to effect a seal. As is well known, the use of latex as a sealing material has the advantage that when the portion of the flap and the portion of the envelope body to which the latex has been applied, are brought into contact with each other and pressure applied thereto, the flap will be effectively sealed to the body of the envelope, without the requirement of the application of moisture to the latex material. The use of latex as an envelope sealing material is well known, however, it has been found that known methods and techniques are not capable of applying the latex at a sufficient rate of speed to justify the costs involved in using latex. For instance, present day equipment is capable of gumming envelopes at a speed of approximately 12,000 envelopes per hour, of course, depending on the envelope size and amount of latex applied. Although this may appear to be a high rate of speed, it should also be borne in mind that in the United States alone, roughly 100 billion envelopes are manufactured each year. Thus a great number of machines are required for applying sealing material, and hence it would be most advantageous if increased production could be obtained from each machine. To a great extent the limitation on the number of envelopes that may be processed by each machine is limited by the use of conventional forced air heating means for drying the latex after it has been applied to the envelope. Another shortcoming of present equipment and techniques is the difficulty that has been encountered in the proper application of the latex to the envelopes. As an example, it is extremely undesirable to have the latex, which is applied to the envelope flap and/or body, extend completely from one end of the flap to the other edge thereof because the latex has a tendency to bead or run over the edges, and thus produce a messy, unsatisfactory envelope which, when the envelope is sealed, will have excess visible latex. In addition, the improper application of latex to the envelope body or flap may result in beads along the edges of the envelope body or flap, thereby requiring the slower drying of the latex, which again reduces the production capability of conventional apparatus. Still furthermore, it has been found that when unsealed envelopes are stacked, they will not stick together if the sealing material terminates inwardly of the envelope edges. Thus, by carefully controlling and ensuring that the latex is disposed back from the edges of the envelope, it is easier for the operator to feed the envelopes through a printing or packaging machine.
Another disadvantage of present equipment and techniques for the application of latex to envelopes is the occurrence of bubbles or voids in the latex which also results in an unattractive envelope, as well as one which may not seal perfectly.
Still another shortcoming of known equipment and techniques is the necessity for the operator to load the blank envelopes into the apparatus at one end of the machine, and then unload the apparatus at the opposite end of the machine, whereby the speed of operation of the machine is determined by the efficiency of the operator in traversing the distance between the opposite ends of the machine or using more than one operator.
In other known apparatus, there is also the arrangement wherein a plurality of conveyors are provided, one for each step in the process, thereby necessitating the transfer of the series of envelopes from one conveyor to other conveyors, which results in extremely large machines that occupy large areas, and also require the operator to traverse long distances in order to load and unload the envelopes.
Accordingly, it is the object of the subject invention to overcome the shortcomings of known apparatus and methods for applying sealing material to envelopes, and more particularly to provide a new and approved method and apparatus for applying latex to envelopes in a rapid, efficient, and neat manner, which method and apparatus can readily and easily handle various size envelopes at greater speeds than heretofore achieved.
It is another object of the subject invention to provide a new and improved method and apparatus for achieving increased rates of production of applying sealing material to envelopes, while achieving better quality of the resulting application of latex material to the envelopes in order to obviate running, voiding, bubbling or blistering of the latex material.
It is a further object of the subject invention to provide an apparatus and method which employs a dielectric dryer for drying the sealing material applied to the envelope in order to achieve greater production rates.
It is still a further object of the subject invention to provide a method and apparatus for applying sealing material to envelopes wherein the envelopes are conveyed in a continuous process by a single conveyor means thereby greatly reducing the cost of manufacture of the apparatus.
Still another object of this invention is to provide a method and apparatus for applying sealing material to envelopes wherein a continuous conveying means is employed for conveying the envelopes, and wherein the operator feeds and removes envelopes from the conveying means from a single location.
It is a further object of the subject invention to provide a new and improved method and apparatus for applying sealing material to envelopes wherein a continuous conveying means is employed and is capable of conveying two linear arrays of envelopes at the same time in order to obtain increased production.
It is another object of the subject invention to provide a new and improved apparatus for applying sealing material to envelopes wherein the envelopes are fed into the machine in their normally packaged condition in which the closure flap is folded against the body portion, and which method and apparatus includes means for unfolding the flap preparatory to the application of adhesive to the undersurface of the closure flap.
Still another object of the subject invention is to provide a new and improved method and apparatus for applying sealing material to envelopes wherein dielectric dryer means are provided for rapidly and efficiently drying the adhesive applied to the envelopes, which dielectric drier means includes an alternating arrangement of a plurality of a generally parallel electrodes and ground conductors, connected to a central power supply.